A head mounted display as a wearable device enables network information or the like on the Internet to be usually obtained at a part of the field of vision, thereby enabling various applications to be developed. In the head mounted display, video is usually displayed at a part of the field of vision. Therefore, it is necessary to cause external world information other than the video to be easily acquired, that is, a see-through function is necessary.
For example, in PTL 1, a member which forms an eyepiece aperture holding section has a see-around function while having a width of 4 mm or less in a projection section taken in the direction of the visual axis of a user within a range of 10 mm or more from the eyepiece aperture to the root except a partial protrusion. In addition, a display device is disclosed in which the member which forms the eyepiece aperture has the see-through function while having a width of 4 mm or less in the projection section taken in the direction of the visual axis of the user.
In addition, the optical efficiency is improved by equalizing the brightness distribution of an illuminating optical system. Therefore, for example, PTL 2 discloses a structure in which a diffraction section is provided in an area on the side of the incident opening of the sidewall surface of a light pipe.